Abstract: The flight ability and changes of flight muscle structures after flight of cotton bollworm (CBW) Helicoverpa arrnigera (Htibner) were systematically tested for thefirst time in China by applying flight mill, wind tunnel and electron-microscope. Based on these data combined with the results of the different diapause and cold hardiness conditions and characteristics of micro-morphology and molecular biolgical markers andCBW populations collected from different cotton regions in China, and division of theirresistance to insecticides, marine trapping data, sources analysis of pollens carried on the heads of CBW moths, as well as the labelling-release-recapture test in small scale, it was confirmed that CBW is a typical species possessing facultative migration ability, andthe CBW source of Liao River Valley Cotton Region, the most early maturing cotton region in Northeast China, might come from Yellow River Valley Cotton Region, and there might be frequent exchanges of CBW populations between neighboring cotton regions. The morphology and distribution of different kinds of olfactory sensilla on CBW antenna were observed. By using GC-EAG and GC-MS, the electro-physiological reactions of CBW to the extracts from different organs of a number of host plants were compared,and the components of volatile allelochemics in these extracts attractive to CBW mothwere determined. It was found that in cotton, most of the attactive allelochemics to CBW are terpenoids, in which the C10H16 terpenes possessing rather weak polarity can attract CBW moth to feed, while the sesquiterpenoids (C₁₅H₂₄) and other allelochemics possessing strong polarity can attract it to lay eggs. Methods for determining the components and contents of secondary metabolites in cotton plant suppressive to CBW, such as terpenoids, tannins and flavonoids were im-proved, the effects and interactions of different kinds of these metabolites on the development and reproduction of CBW were studied. Cross and back-cross methods were adopted to explore the genetic characteristic of resistance of cotton to CBW. On the other hand, artificial methods such as to spray the preparation of Bt transgenic Bacillus oiginally endogenous in cotton for promoting the resistance of cotton to CBW were tried. Finally, the factors causing the outbreaks of cotton bollowrom in China were analysed along four aspects, namely, the climate, nourishment, natural enemies and insecti- cide resistance. It could be said that the drought weather is the most important environmental condition of CBW cataclysm, the increasing fertility, especially the nitrogen fertility, is the main material basis making the CBW problem more and more important,and the unduly use of insecticides is the major man-made factor bringing about CBW population out of control.

Key words: cotton bollworm, migration, diapause, plant allelochemics, secondary metabolites of cotton, resistance to insect, factors of cataclysm